“A raster manipulation unit or ‘wobbulator’ is a prepared television which permits a wide variety of treatments to be performed on video images; this is accomplished by the addition of extra yokes to a conventional black and white receiver and by the application of signals derived from audio or function generators on the yokes.
The unit is a receiver modified for monitor capability; all of the distortions can thus be performed either on broadcast signals or, when the unit is used as a monitor, on images from a live or prerecorded source. Although the image manipulations cannot be recorded directly, they can be recorded by using an optical interface. The patterns displayed on the unit are rescanned; a camera is pointed directly at the picture tube surface and scans the display. The video signal from this rescan camera is then input to a videotape recorder for immediate recording or to a processing system for further image treatment. The notion of prepared television has been investigated by a number of video artists and engineers; this particular set of modifications was popularized by Nam June Paik.”